(54) IMPROVEMENTS RELATING TO MOULD OR CORE-MAKING(71) We, STONE WALLWORK LIMITED, a Company incorporated under the laws ofGreat Britain, of Woolwich Road, London,S.E.7, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: In certain types of mould and core-making machines, moulding or core-making material is introduced into a substantially sealed mould or core box from a magazine by means of pressure in the magazine, normally provided by connecting the magazine to a compressed-air supply.
During transit of the material from magazine to core box, some compressed air will travel with the material. The presence of this air is undesirable and means have been employed for its release. Thus permeable areas in the mould or core-box cavity and/or exhaust slits in the joint face of the box have been provided. The siting of permeable areas is often critical and in many cases the shape of the cavity prevents incorporation of permeable areas in desirable locations.
A further disadvantage is the need for adequate sealing of the box-joint faces and of the engaging faces of the magazine and box. Leakage at either place allows egress of air and material. The latter is usually abrasive, causing wear which is rapidly progressive.
Complex box cavities requiring abrupt changes of direction of material during charging are sometimes difficult to fill, except by the use of high pressure in the magazine. Under this condition the box must be held firmly closed, usually at the cost of large-diameter clamping cylinders and a correspondingly heavy demand for compressed air or hydraulic power.
The present invention seeks to obviate or mitigate the above-mentioned disadvantages.
According to the invention, in a method of charging a mould or core box with mouldor core-making material, air is evacuated directly from the uncharged box and the evacuated box is then charged from a magazine. Preferably the box is not subject to a pressure higher than atmospheric pressure throughout the charging. To this end, use may be made of an open or unpressurized magazine. Alternatively, a pressurizable magazine may be employed and pressurized during at least part of the charging operation, preferably, however, in such a manner that the box is not subject to higher than atmospheric pressure and certainly not in such a manner as to incur the disadvantages referred to above.
During the charging, the pressure in the box is less than atmospheric pressure throughout at least a part of the operation.
By the use of the invention, the need for providing permeable areas in the box cavity is substantially reduced or eliminated and box-clamping forces can be significantly reduced.
The invention further provides apparatus, for carrying out the aforesaid method, comprising, in operative combination with a mould or core box and a magazine from which the said box is charged with moulding or core-making material, means for directly evacuating the box prior to, or prior to and during, charging from the said magazine.
For producing so-called shell moulds, methods and apparatus have been proposed heretofore, for example in United KingdomSpecifications Nos. 1,440,853 and 735,355, in which a box was charged with hardenable material under pressure from a magazine and, after cutting off of the box from the magazine and hardening of a shell of the material in the box by heat, unrequired excess material was removed from within the shell by the application of suction to the box.
By "directly" in this Specification and the appended claims, it is to be understood that the air is evacuated through connnections to the box itself and not by way of a bell or other enclosures containing the box or by way of the magazine or a chute connecting the magazine to the box.
In a preferred arrangement illustrated by way of example in the accompanying diagrammatic drawing, a magazine 1 is charged with moulding material retained by a valve, which is a shutter plate 2 in the example. The magazine has a permanently open top, so that the pressure in the magazine is the atmospheric pressure.
A core or mold box 3 is closed by a piston 4 and the magazine is lowered to engage the top of the box in customary manner. The box has a conventional ejection system, which is enclosed by a cover 5, the operating piston for the ejection mechanism being sealed by a gland 6. The pressure in the box cavity is reduced by means of pump 7, evacuation of air from the box cavity via the interior of the cover 5 and passages 51 being accelerated by a largecapacity vacuum vessel 8. Suitably the evacuation may be such that the pressure is reduced to a value between 25"Hg and 28"Hg, for example. The plate 2 is then opened and material is transferred from the magazine to the box. During the charging operation, atmospheric pressure assists in maintaining a seal at the vertical box-joint face and between the magazine and box.
Should there be imperfections on these surfaces, there will not be leakage of material to the outside, but inward leakage of surrounding air. Abrasive destruction of these faces is therefore avoided. The material reaches the extremities of the cavity easily, as there is no trapped air to be expelled.
By the end of the charging operation, the pressure in the box 3 will at most not exceed the atmospheric pressure.
After charging, the box 3 is isolated from the vessel 8 and pump 7 by closing a valve 9, the plate 2 is closed and the mould or core is thereafter subjected to conventional treatment, e.g. chemical or thermal hardening, ejection and removal.
In place of the open magazine 1 illustrated, use may be made of a closable magazine which can be pressurized in known manner by connecting it to a source of compressed air. In this case also, the charging operation should be so performed that the pressure in the box 3 is still not in excess of, if not below, the atmospheric pressure at the end of the operation. Indeed, provided that the box 3 is evacuated before the charging operation, the pressure therein may rise above atmospheric pressure by the end of that operation, although preferably this is not allowed.
WHAT WE CLAIM IS:- 1. A method of charging a mould or core box with moulding or core-making material, wherein air is evacuated directly from the uncharged box and the evacuated box is then charged from a magazine.
2. A method according to claim 1, wherein the box is not subject to a pressure higher than atmospheric pressure throughout the charging.
3. A method according to claim 1, wherein the magazine is an open or unpressurised magazine.
4. A method according to any one of claims 1 to 3, wherein evacuation of the box is continued during the charging operation.
5. A method according to claim 1 or claim 4 as referred to claim 2, wherein the magazine is pressurised during part at least of the charging operation.
6. A method of charging a mould or core box substantially as hereinbefore described.
7. Apparatus for carrying out the method in any one of the preceding claims, comprising, in operative combination with a mould or core box and a magazine from which the said box is charged with moulding or core-making material, means for directly evacuating the box prior to, or prior to and during, charging from the said magazine.
8. Apparatus for carrying out the method claimed in any one of claims 1 to 6 substantially as hereinbefore described with reference to the accompanying drawing.
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